What Is Solar Panel?

What is a solar panel?

A solar panel is the prefabricated assembly that converts sunlight to DC electricity. Inside the panel, between a tempered glass front and a polymer backsheet, sit roughly 60 to 144 solar cells wired in series. The cells themselves are thin slices of silicon doped to create a one-way path for electrons released by absorbed photons. Encapsulant (typically EVA) holds the cells in place and protects them from moisture. An aluminium frame and a back-side junction box complete the assembly.

The output of a panel is DC electricity, voltage and current set by the cell arrangement. Indian residential installations in 2026 mostly use modules in the 540 to 600 Wp class with 144 half-cut cells. Commercial and utility-scale projects often use modules above 600 Wp with bifacial glass-glass construction.

The panel is the most visible part of any solar plant, but it is not the only part. The inverter, mounting structure, cables, combiner box, AC/DC disconnects, and the bi-directional meter complete the system. Of the total project cost, the module typically accounts for 40 to 50 percent.

Why solar panels matter

The solar panel is the asset that produces every kWh the system ever delivers. Module quality, technology choice, and warranty terms set the ceiling on what the project can ever earn. Everything else (inverter, BOS, design) is about how efficiently and reliably that ceiling is delivered to the grid or the load.

For EPCs, module selection is the most consequential decision in the project. A 0.4 percent per year better degradation rate compounds to roughly 8 percent more cumulative kWh over 25 years, which can shift payback by six to nine months on a residential project. Module cost per kWp also drives most of the per-kWp competitive pricing.

For consumers, the panel is the only part of the system most buyers can visually inspect. That makes brand, model, and visible build quality outsized in purchase decisions, even though performance is determined by less visible factors (cell technology, temperature coefficient, manufacturer process control).

For policy, modules are the load-bearing element of India's solar manufacturing push. ALMM, DCR, and the BIS certification regime exist to channel demand toward Indian-made modules and ensure a minimum technical floor.

How a solar panel works

1. Sunlight hits the cell. Photons in sunlight strike the silicon surface.
2. Electron release. Photons with enough energy free electrons from the silicon, leaving 'holes' behind. The cell's p-n junction creates a one-way path that drives electrons to one side and holes to the other.
3. DC current. Electrons flow through the cell's metallic contacts and into the external circuit, producing direct current.
4. Series wiring. Cells within a module are wired in series so the voltage adds up. Modules in a string are also wired in series for higher string voltage.
5. Combiner box. Multiple strings combine in parallel at the combiner box, increasing current.
6. Inverter. The inverter performs Maximum Power Point Tracking (MPPT) to extract the best operating point from the modules and converts DC to AC at grid frequency.
7. Net meter. The AC output feeds the building load. Surplus exports through the bi-directional meter to the DISCOM under net metering.

The process is silent, has no moving parts inside the modules, and runs from sunrise to sunset every day with no operator intervention.

Real example: a typical 5 kWp Indian rooftop module layout

Setup. A 5 kWp residential rooftop in Indore. Customer chose monocrystalline TOPCon modules rated 565 Wp each.

Module count. 5,000 Wp ÷ 565 Wp per module = 9 modules (rounded; final design used 9 × 565 Wp = 5,085 Wp, a touch over the rated 5 kWp).

Layout. Three strings of three modules each, mounted on a 15-degree tilt aluminium structure facing south. Roof shadow from a water tank affected one corner; that area was left unutilised rather than risk shading.

Wiring. Each string runs at about 120 to 130 V DC. The three strings combine in parallel at a combiner box, feeding a 5 kW AC string inverter (DC/AC ratio 1.02).

Expected annual generation. 5.085 kWp × 1,540 kWh/kWp/year × 0.79 Performance Ratio = 6,189 kWh/year.

Module cost contribution. The 9 modules cost about ₹83,000 of the ₹2.1 lakh total project cost, or roughly 40 percent.

Benefits of modern solar panels

• 25- to 30-year output warranty. Long-tail revenue is contractually protected.
• High and rising efficiency. Mainstream Indian module efficiency crossed 21 percent in 2025; premium TOPCon and HJT modules exceed 22.5 percent.
• Low maintenance. Cleaning and visual inspection are usually sufficient. No moving parts to service.
• Modular scaling. Systems scale linearly: more panels mean proportionally more kWh.
• India-made supply. ALMM and DCR ensure ready availability of Indian-certified modules across price tiers.
• Predictable degradation. Linear degradation curves let EPCs and lenders model 25-year cash flows with confidence.
• Improving temperature behaviour. Newer cell technologies have lower temperature coefficients, useful in Indian summer conditions.

Limitations and challenges

Output is irradiance-dependent. No sun, no electricity. Cloudy days, monsoons, and short winter days reduce generation.

Temperature sensitivity. Silicon modules lose output as cell temperature rises. Indian summer rooftops hit 55 to 65 degrees Celsius on the back of the module.

Soiling. Dust, pollution, and bird droppings cut output by 3 to 10 percent without cleaning.

Shading. Even partial shade on one cell can cut a string's output disproportionately. Microinverters or DC optimisers help but cost more.

Roof and structural considerations. Older Indian residential roofs may need waterproofing and structural reinforcement before installation.

Recycling and end-of-life. India is still building module recycling infrastructure. Year-25 retirement is starting to become a real planning question.

Hail and storm risk. Most modules meet hail-impact tests but localised severe hailstorms have caused fleet damage in northern and eastern India.

Solar panels in India

India's module manufacturing has expanded sharply since 2020 under the Production-Linked Incentive (PLI) scheme and DCR-driven demand. Key facts at the time of writing:

Aspect	Status
Dominant cell technology in 2026	Monocrystalline PERC, transitioning to TOPCon
Typical residential module	540 to 600 Wp, half-cut, monocrystalline
Typical commercial / utility module	590 to 720 Wp, bifacial, glass-glass construction
Mainstream efficiency	20.5 to 22.5 percent
ALMM-listed manufacturers	Domestic and approved international
DCR requirement	Indian-made cells and modules for PM Surya Ghar and government tenders
Major Indian Tier-1 manufacturers	Waaree, Adani Solar, Tata Power Solar, Vikram Solar, Premier Energies
Typical residential cost	₹14 to ₹22 per Wp (modules only)

Quick facts

Term	Solar Panel (Solar Module)
What it does	Converts sunlight to DC electricity via the photovoltaic effect
Standards	IEC 61215, IS 14286, BIS certification
Typical Indian residential module	540 to 600 Wp, monocrystalline TOPCon or PERC
Efficiency	20.5 to 22.5 percent (mainstream); 23 percent+ (premium)
Warranty	25 to 30 years of output (typically 80 to 85 percent at year 25)
Degradation rate	0.5 to 0.8 percent per year
Module cost share	40 to 50 percent of total system cost
Required for PM Surya Ghar	ALMM-listed, DCR-compliant Indian-made modules

Common mistakes about solar panels

1. Buying purely on per-watt price. Cheaper modules with poor temperature coefficient and weak warranty deliver less lifetime kWh.
2. Treating polycrystalline as currently viable for new installs. Mono PERC and TOPCon dominate in 2026. Poly is legacy.
3. Ignoring shading at site survey. A single shaded cell can cut its string's output sharply. A careful survey saves design surprises.
4. Skipping ALMM verification. Non-ALMM modules disqualify PM Surya Ghar and most government tender installs.
5. Assuming "Indian-made" automatically means DCR-compliant. DCR requires Indian-made cells and modules. Imported cells in Indian-assembled modules do not qualify.
6. Forgetting to factor degradation in payback. Year-25 output is roughly 80 to 85 percent of year-1. Honest 25-year IRR uses the degradation curve.
7. Choosing the wrong tilt or orientation. South-facing at site latitude (or close) is optimal in India. East and west variations cost 5 to 15 percent of annual yield.
8. Ignoring the back-side bifacial gain. Bifacial modules can pick up 5 to 15 percent extra yield on light-coloured roofs and ground-mounted installs.
9. Cleaning aggressively with hard water. Mineral deposits etch the glass over time. Use soft water or RO-treated water for cleaning.
10. Treating panel warranty as system warranty. The module warranty is from the manufacturer. The system workmanship and BOS warranty is from the EPC. They are separate.

Key takeaways

• A solar panel converts sunlight to DC electricity using silicon cells, glass, encapsulant, and backsheet.
• "Panel" and "module" mean the same thing in Indian practice.
• Indian residential installs in 2026 mostly use 540 to 600 Wp monocrystalline TOPCon or PERC modules.
• Module cost is 40 to 50 percent of total project cost.
• Modules carry 25- to 30-year output warranties; degradation is roughly 0.5 to 0.8 percent per year.
• For PM Surya Ghar, modules must be ALMM-listed and DCR-compliant.
• Choose on cost per Wp, temperature coefficient, degradation rate, and warranty terms, not visual aesthetics alone.

Frequently Asked Questions

Sources

• IEC 61215. Crystalline silicon photovoltaic module qualification testing.
• IS 14286. Indian standard for terrestrial photovoltaic modules.
• MNRE. Approved List of Models and Manufacturers (ALMM) for modules and inverters. mnre.gov.in
• BIS (Bureau of Indian Standards). Certification standards for PV modules.
• NREL (National Renewable Energy Laboratory). Photovoltaic technology overview and performance modelling.
• Indian module manufacturer technical datasheets. Waaree, Adani Solar, Tata Power Solar, Vikram Solar, Premier Energies.
• National Institute of Solar Energy (NISE). Module testing and certification methodology.